1. Field of the Invention
The present invention relates to trocars and similar devices used in surgical procedures. More particularly, the present invention is directed to an improved trocar and cannula assembly for use in such procedures.
2. Background of the Prior Art
Although there is a long history of employing a variety of tools to assist in creating openings in a human or animal patient during surgery, recent improvements in surgical technology and techniques has spurred renewed interest in methods of establishing and maintaining such openings in a patient.
Traditionally, a sharp trocar instrument has been employed to produce an incision in a patient, which is then often followed by the insertion of a cannula to provide an orifice through which necessary drainage or surgical techniques could be performed. One of the major concerns in introducing a trocar into a patient is that the force of incision often produces a considerable follow-through force which may result in accidental puncture wounds to internal organs.
As a result to this concern, recently a variety of new apparatus have been introduced to attempt to improve upon this basic procedure. One of the major areas of interest has been in attempting to provide an automatic safety shield to surround and protect the trocar tip immediately upon entry into the patient. Examples of such devices are illustrated in U.S. Pat. Nos. 4,535,773 issued Aug. 29, 1985, to Yoon, 4,601,710 issued Jul. 22, 1986, to Moll, 4,654,030 issued Mar. 31, 1987, to Moll et al., 4,902,280 issued Feb. 20, 1990, to Lander, 4,931,042 issued Jun. 6, 1990, to Holmes et al., and 5,066,288 issued Nov. 19, 1991, to Deniega et al. Although these existing devices are definitely a major improvement over previous trocar apparatus, they continued to be plagued with a number of problems.
Foremost among applicants' concerns with the present safety-shielded trocar devices is that the shields do not activate soon enough. In every commercially available shielded trocar known to applicants, the safety shield comprises essentially a tubular unit which is activated to surround the entire outside of the trocar's piercing end upon insertion. Examples of such designs are illustrated in each of the above patents. Even though such shields are generally effective at guarding the trocar's cutting tip, when these units are inserted through the patient's skin tissue the tissue surrounding the external safety shield offers significant resistance and impedes shield activation. As a result, the entire piercing end of the trocar and the shield normally must be fully inserted before the shield can activate. As a result, if extreme care is not exercised the incision force often can follow-through to cause serious internal injury in the instant before the safety shield can achieve a fully extended position.
The use of an external trocar safety shield also tends to present a myriad of other problems. First, the external shield tends to provide an additional impediment to insertion, thus requiring greater incision force and compounding the risk of follow-through injury. Second, the force of the safety shield passing through the skin tissue often results in tearing and other damage at the incision. In addition to needlessly increasing the size of the surgical wound, this also tends to compromise the foundation of a cannula and may lead to undesirable leaks of fluids and gases during the operation. Third, a number of physicians have complained that the recoil from the "snapping" of the safety shield into position at almost the same moment as the trocar insertion tends to disorient them as to the precise location of the trocar after insertion. This results in wasted time and effort to re-orient the trocar and greater risk of internal damage during the period of re-orientation.
Another problem with existing trocar devices is that many employ complicated actuation and locking mechanisms requiring far too much expense and often necessitating costly mated trocar and cannula assemblies. This undermines attempts to recycle those elements (e.g. the cannula) which normally could be sterilized and reused.
Accordingly, it is a primary object of the present invention to provide a trocar apparatus which activates a safety shield with full trocar tip protection before complete insertion of the piercing end of the trocar.
It is a further object of the present invention to provide such a trocar apparatus which is easily inserted and creates a limited incision, thus leaving a minimal surgical wound, providing better stabilization of a cannula or other instruments, and assuring a better seal for gases and liquids during the surgical procedure.
It is another object of the present invention to provide such a trocar apparatus which minimizes recoil from activation of the safety tip protector apparatus so to avoid disorientation of the physician and damage which may be cause by the safety shield itself.
It is still another object of the present invention to provide such a trocar apparatus which has a simple yet effective tip protector locking mechanism, limiting costs while permitting a wider variety of uses, including use with different cannula systems, such as reusable cannula systems.
These and other objects of the present invention will become evident from review of the following specification.